The judge is expected to make a reserved decision on Thursday.
Mr Shearer had scoffed at Mr Key for accepting Mr Banks' assurances that his 2010 mayoral campaign donations disclosure was within the law, after Kim Dotcom's $50,000 donation was listed as anonymous. Mr Banks has maintained he didn't know about the donations. Mr Key said Mr Shearer was quick to criticise him for accepting Mr Banks' word, but when put in a similar situation he had also "simply taken the guy at his word".
Mr Key said he was not questioning Mr Jones' word, but he had been cautious before criticising others when he was in Opposition.
"And Shearer hasn't been."
Mr Key said Mr Jones needed to explain why he'd made the decision to approve the application. "It's important to understand it's Bill Liu [Yan] on trial, not Shane Jones. But it'll be interesting to see what comes out as a result of that trial."
Shane Jones spoke out for the first time on Radio Live this morning, defending his decision to grant Yan's citizenship.
"I had that file for well over a month, not, as has been alleged, overnight," Jones told host Marcus Lush.
"The submissions that were given to me were both from the Crown officials and a submission by one of New Zealand's most imminent QCs. I considered the issue, and then on humanitarian grounds, because the guy had a wife and kids ... I made what was a difficult decision and I stand by that decision.
"But the suggestion that somehow I got the file, had a shower and the next day approved it, is wrong."
Mr Jones would not reveal what the humanitarian grounds were, but said he would speak more on the case once the judge has made his decision.
"There were a host of allegations being made against the man - none of them were proven. Not a single thing has been proven, as I recall, which is why in one sense, out New Zealand court system is able to test the veracity of both the information that this man gave and the anxieties and concerns the officials have.
Mr Jones said he "can't recall" meeting Mr Yan, but said it was possible he may have met him "once or twice, if at all" at various functions.
He "did not know" if Mr Yan was well-connected to the Labour Party.
"Quite frankly, the allegations that are swirling around ... let them be sorted out in the court," Mr Jones said.
"The essential information that has been tested in the court is - is this man who he says he is. That's what this is about. That decision is going to be issued at some point in time by Justice Brewer."
Mr Shearer left the door open to act against Mr Jones if further information came to light that showed Mr Jones had misled him.
His statement emphasised that he was relying on Mr Jones' account of the decision and information held by Mr Jones, but he had not been able to check departmental information. He had also taken the step of checking with other Labour MPs who knew about the issue, understood to include David Cunliffe and Clayton Cosgrove.
Mr Shearer said it was not uncommon for ministers to act against the advice of officials and the process Mr Jones went through was "considered and proper."
Mr Jones had assured him he had gained no benefit from the decision. Mr Shearer said Mr Jones was not a friend of Yan and had not attended a citizenship ceremony organised for Yan by former Labour MP Dover Samuels at Parliament.
The decision had been delegated to Mr Jones because then Internal Affairs Minister Rick Barker also knew Yan and had a potential conflict of interest.
